TUESDAY, Sept. 25 (HealthDay News) -- People with chronic obstructive pulmonary disease (COPD) are more likely to sleep poorly than their peers without this serious condition, a new study confirms.

Their sleep quality may be associated with low oxygen levels in their arterial blood, the researchers found.

"Patients with COPD frequently report fatigue, sleepiness and impaired quality of life," said Walter McNicholas, a professor in the department of respiratory and sleep medicine at St. Vincent's University Hospital in Dublin, Ireland. "The study carried out by our group, which has been researching sleep and breathing for more than 25 years, showed that such patients experience poor sleep quality, which may contribute to these debilitating symptoms."

People with COPD have difficulty breathing because of lung damage, usually caused by smoking.

The researchers conducted a secondary review of two previously published studies involving more than 100 people with moderate to severe COPD. The patients were on average 66 years old, and 67 percent were men. All were current or former smokers.

The research was undertaken to examine the effect a long-acting bronchodilator (an inhaler that relaxes lung muscles and opens airways) had on nighttime oxygen saturation.

The current study, published in the October issue of the journal Respirology, found that it took COPD patients longer to fall asleep and that they spent less of their time in bed sleeping than others their age without lung disease. They also had a less deep sleep.

"However, sleep quality in COPD is determined by several factors and further studies on this topic are necessary to fully evaluate the relationship," he said. "This may identify therapeutic interventions that might improve the overall quality of life in COPD patients."

Although the research discovered an association between COPD and poor sleep quality, it did not prove the existence of a cause-and-effect relationship.